The prior art pertaining to impact printers incorporates the utilization of a tractor drive assembly. The tractor drive assembly has a number of pins which drive a continuously connected sheet of perforated fanfold paper. Along the edge of the fanfold paper are a plurality of openings which have been punched in the edge of the paper. The openings are received over a series of pins on the tractor belt. As the tractor belt moves, the pins engage the openings in the edge of the paper and drive it. As the paper is being driven, the impact printer shuttle moves backwardly and forwardly across the paper to allow the impact hammer tips to imprint upon the paper through means of an ink ribbon.
Easy removal of the paper or document that has been printed upon from the tractor prior to the document exiting the tractor, has not been accomplished to date. Fundamentally, the paper has to travel completely through the printer and then be removed by tearing it along the perforations in the fanfolds of the paper. This causes a waste of paper. Oftentimes, that which is to be printed only has a minimum number of lines. If the paper can not be removed until it has travelled completely through the tractor and in most cases through the printer itself, it creates inefficiencies and waste.
This problem necessitates an excess use of paper, as well as creating operator difficulties. The invention hereof overcomes the difficulties of the prior art by allowing removal of the paper prior to the document exiting the tractor. This is done by opening an upper lid independently so that the document or paper can be removed from the printer while it is closer to the print station. The conformation of the invention is in the form of a split tractor clamp or lid. The lower lid maintains the drive pin engagement with the paper drive holes or openings in the side of the paper. The foregoing preserves the paper alignment in its proper location.
With both lids closed, a full complement of drive pins drives the paper in the openings along the edge. The upper lid and lower lid guide and support the paper in the same manner as a conventional single lid tractor. However, when opening the combined lid by pulling on the lower lid, the split tractor lid functions as a single lid. They open by virtue of the lower lid serving to engage the upper lid. This is caused by a lip between the upper and lower lids engaging one another so that the upper and lower lids open simultaneously when the lower lid is pulled open.
The features and objects of the invention in part reside in a lower tractor lid which is sufficiently large enough to maintain tractor pin engagement with the paper drive holes.
Another feature is to provide an upper access lid that can function independently from the lower lid. This provides for independent removal of shortened paper lengths by tearing the paper along perforations in the fanfold paper.
Another object and feature of the invention is to provide a commonly hinged access for both lids so that each lid can operate independently or together. To enhance this operation, a spring or other device to hold the lids in closed relationship is provided.
A magnet spring latch or other device can hold the upper lid closed, and/or can be attached to the lower lid to provide for securement thereof.
The functions of the split lid of the tractor will be appreciated when the description hereinafter is seen in light of the drawings as to its configuration and function.